persistent graphics 1

[danielprovin]

I am having problems trying to modify the persistent graphics of a window (the window already exist) using it hWnd
I can already paint on the window, but another window goes on top of this window, it erases the paint

 

[LiquidBinary]

What do you mean by the window already exists? I take it that you did not create the window that you are painting to? The problem resides in the fact that the window only knows how to re-paint it's controls, background color etc...it has no idea what you want to re-paint...be it a bitmap or just simple GDI output. To correctly restore the desired client area output you must handle the WM_PAINT message...of course this is assuming raw api programming...more info would help. Mike L.G.
mlg400@linuxmail.org

 

[danielprovin]

Yes, the window is a PictureBox object from VB, but I will create an activeX_dll that will modify that PictureBox.
I tried to handle the WM_PAINT message, re-painting the graphics, but it didn't work

that's what I use:

LRESULT CALLBACK WndProc(HWND hWnd, UINT uMessage, WPARAM wParam, LPARAM lParam)
{
switch(uMessage)
{
case WM_PAINT:
{
PAINTSTRUCT ps;
BeginPaint(hWnd,&ps);
if (bCopiaJanela) PintaCopiaJanela(ps.hdc);
SetBkMode(ps.hdc, TRANSPARENT);
SetTextColor(ps.hdc, RGB(255,0,0));
TextOut(ps.hdc, 100,100, "Press SPACE", 11);
EndPaint(hWnd,&ps);
break;
}
}
return DefWindowProc(hWnd,uMessage,wParam,lParam);
}

 

[LiquidBinary]

Try returning 0 after WM_PAINT executes...

LRESULT CALLBACK WndProc( HWND hWnd, UINT uMessage,WPARAM wParam,LPARAM lParam )
{
PAINTSTRUCT ps;
HDC hdc;
switch( uMessage )
{
case WM_PAINT:

hdc=BeginPaint(hWnd,&ps);
if ( bCopiaJanela )PintaCopiaJanela( hdc );
SetBkMode( hdc,TRANSPARENT );
SetTextColor( hdc,RGB( 255,0,0 ) );
TextOut( hdc,100,100,"Press SPACE", 11);
EndPaint( hWnd,&ps );

return 0;
}
return DefWindowProc(hWnd,uMessage,wParam,lParam);
} Mike L.G.
mlg400@linuxmail.org

 

[MrDwight]

Sounds like you are having a similar problem to what I'm trying to solve. (See my post "Dialog Box: Bitmap gets erased when a screen is dragged over.&quot
I have my own application, but the problem exists for my dialog box, too.

LiquidBinary, thanks for the tip on the WM_PAINT message, I'll check that out.

DMF

 

[danielprovin]

This code have worked on THE application, but when I tried to implement a dll that gets the hwnd from a window of another application, it won't hook to process the WM_PAINT message
is there any way to make it goes thru the dll?

 

[danielprovin]

I found that on MFC applications, u can't use WndProc to handle the WM_PAINT messages, u need to use the AfxRegisterWndClass function, but the help didn't help me that much

so, anyone know something about handling window messages on a MFC dll?

thanks
Daniel

 

[danielprovin]

I had finally found a happy end to my problem
What I had to do was to subclass the existing window to a new function to handle the messages (like WM_PAINT) using
SetWindowLong with the hwnd, GWL_WNDPROC argument, and the name of the new function to handle messages, than it handle only the messages to that specific hwnd.

hope it helps other people
Daniel

 

[MrDwight]

Good advice, thanks for the update!